Re: [Discuss-gnuradio] USRP1 questions

[osama mohamed]

> Date: Mon, 12 Dec 2011 08:07:57 -0800
> From: address@hidden
> To: address@hidden; address@hidden
> Subject: Re: [Discuss-gnuradio] USRP1 questions
>
>
>
> On 12/12/2011 01:52 AM, osama mohamed wrote:
> >
> > hi all,
> > i am using USRP1 with basic tx and rx boards and i have been suffering some problems recently so i hope you could answer the following questions(even if not all of them)
> >
> > Q1:
> > when i run the examples tx_timed_samples.cpp and tx_burst.cpp i don't
> > get any output i tried various sampling rates and amplitudes but they
> > still didn't produce any output if there is a certain configuration
> > (i.e. sampling rate and amplitude) that works kindly inform me also i
> > would like to know the output i am expected to see?
> >
> >
>
> Those are examples apps to demonstrate API usage. See tx waveforms or tx
> samples from file for examples that transmit.
>
> > Q2: i would like to tx a signal by setting the NCO frequency on the
> > codec chip through the class codec_ctrl instead of using the PLL, is
> > this doable or not and ,if yes should i use the class multi_usrp or i
> > have to jump to the lower level class usrp1_impl?
> >
> >
> If you have basic TX and usrp1, the only frequency translation occurs in
> the codec. There is no PLL.
>
> > Q3: can i use the low level class usrp1_impl to do the same
> > functions of the examples tx_timed_samples.cpp and tx_burst.cpp
> > through setting the frequency tuning word of the codec through the class
> > codec_ctrl ?
> >
> >
>
> The implementation is not exposed. You will need some "creative" coding
> if you want to access the internal objects.
>
> What do you think is missing in the "multi_usrp" wrapper?
>
> > Q4: as i understand from the constructor of the class usrp1_impl the
> > sampling rates of the tx path are automatically detected and assigned
> > through this constructor is this true or i have to set them through a
> > certian function?
> >
> >
>
> You should manually set the desired sample rate through the API.
> See
> http://files.ettus.com/uhd_docs/doxygen/html/classuhd_1_1usrp_1_1multi__usrp.html#ab8bc17744d3ee94b7c5cdcb75457bd6b
>
> -Josh





hi Josh,
thanks a lot for your support.

the problem with the "multi_usrp" wrapper is that if i use another board for example WBX it will generate the desired frequency through the PLL except

for frequencies less than the minimum threshold (which is as i remember 62 MHZ for WBX) so in the later case it will set the PLL to the minimum

frequency (i.e. 62 MHZ) and will compensate the difference through the NCO (as i understand)

i want to do the same by myself even if the target frequency is in the supported range by the WBX (for example : i want to set the PLL to 935 MHZ and

tune the NCO by +or - 44MHZ to get the up and down link ranges of the GSM system ), the reason for using the NCO instead of the PLL is that the NCO

tuning is instantaneous unlike that of the PLL which takes about 200 micro secs

i think this request is not supported by the "multi_usrp" wrapper ??

thanks,
osama riad